1. Technical Field
This disclosure relates generally to adaptive control for a gas turbine engine and, more particularly, to adaptive control that at least partially compensates for off-nominal engine operation.
2. Background Information
Generally, a control algorithm for a gas turbine engine uses an on-board model of dynamics of the engine during nominal operation. A control law using the on-board model may include certain performance margins to accommodate slight dynamic variations associated with manufacturing tolerances, normal wear, and normal environmental conditions.
Some advanced control algorithms include fault detection schemes that compensate for more significant dynamic variations. One example of such a fault detection scheme requires the control algorithm to detect a fault, isolate the fault, and identify the fault before compensating for the fault. In order to detect the fault, one or more measured parameters must be greater than a predetermined threshold. Selection of such a threshold can be difficult, however, due to the inherent compromises between fault detection and fault accommodation. For example, while greater threshold levels can produce fewer false positives, more faults remain undetected and, thus, uncompensated. In contrast, while lower thresholds increase fault detection and compensation, the rate of false positives also increases.
There is a need in the art, therefore, for a continuously adaptive control system operable to control a gas turbine engine during both nominal and off-nominal operation conditions, without requiring fault detection, isolation and/or identification.